The present invention relates generally to digital radio communications systems with multipath fading channels, and more specifically to multipath fading diversity reception suitable for applications where deep fade occurs frequently.
Interference from frequency modulation sources can be treated as a narrow band signal if PSK or QAM digital microwave channels are designed to transport high speed signals. However, interference from other sources on multipath fading channels is treated as wideband signals. For multipath fading channels in which deep fade occurs frequently, diversity reception and adaptive equalization are used as indispensable elements, and on long haul digital transmission routes such as out-of-sight transmission, the use of matched filters and decision feedback equalizers is known.
However, prior art diversity receivers are not capable of combining desired signals either at a maximum amplitude ratio or in an in-phase relationship during a deep fade in which interference simultaneously arises from an undesired source.